I don't think it depends on the number of airports you have flown to. If you pick 10 airports in Europe that are, in one way or the other, special, then the job could be much more challenging than flying to 30 airports where you go in and out with no problems at all.
And there is another challenge: if you fly to a limited number of airports, you get to know them pretty well after some time. Still you have to maintain the same level of alertness whether it is your first or your 50th approach into the very same airport. Being able to do so certainly adds to your proficiency.
About your second question: why should 3 years of short-haul experience be too little?